Allen-Bradley 1771-IGD is an 8-point TTL input module for the PLC-5 1771 I/O system, delivering eight digital inputs that accept TTL-level signals (0–5 V) and report their states to the CPU via the 1771 backplane using the 1771-WH wiring arm. It draws power from the backplane’s +5 V supply for TTL logic and includes a protective fuse to guard both the +5 V rail and input terminals if voltages exceed about 6 V DC or are reversed/AC. The backplane current load is typically around 130 mA, and the module is specifically described as an 8-point TTL input module within Allen-Bradley’s 1771 I/O family.
